→ a88241050 :x<e^(x-1) 10/19 22:03
推 j0958322080 :1 = lne ---> ln(xe) < x ---> x<e^(x-1) 10/19 22:22
推 jacky7987 :let f(x)=x-ln(x)-1 f'(x)=1-1/x>0 if x>1 10/19 22:22
→ jacky7987 :and f(1)=0 10/19 22:23
推 math1209 :看面積. 10/20 08:53
→ Sfly :the same to prove 1+x<e^x, x>0. 10/20 13:17